Production of lubricating greases from oxo esters



United States Patent O PRODUCTION OF LUBRICATIN G GREASES FROM OX ESTERS Arnold I. Morway, Rahway, Frederick Knoth, In, Sayreville, and Jefirey H. Bartlett, Westfield, N. J. assignors to Esso Research and Engineering Company, a corporation of Delaware Application October 25, 1952,Serial No. 316,922 7 Claims. (01. 2s2-35 The present invention relates to a new method of making lubricating greases and to greases produced by this method. More particularly, the invention pertains to an improved grease-making process for the production of new and improved lubricating greases of high dropping point and soft consistency over a wide temperature range.

In brief compass, the invention provides for subjecting a mixture of a high molecular weight olefin with a low molecular weight alcohol to the Oxo-ester synthesis, that is a catalytic carbonylation reaction with carbon monoxide under pressure to form directly an ester of the low molecular Weight alcohol with the acid carbonylation product of the olefin charged; forming a grease-making soap from the acid radical of this ester and incorporating the soap formed into a lubricating oil to convert the latter into grease. It is desirable to combine this soap with a suitable metal salt of a low molecular weight aliphatic acid.

Prior to, the present invention, soap-thickened greases of desirable hardness characteristics and high dropping points, i; e. greases melting above about 400 F. and having a smooth soft consistency over a wide temperature range have been known. These greases have been prepared by the saponification of rapeseed oil with an excess of alkali in a lubricating oil at temperatures of about 480500 F.

The desirable combination of excellent qualities of these greases 'was believed to be due largely to the use of glycerides of C22 long-chain acids, such as erucic acid,

as the source of the soap. Rapeseed oil and the brassidicfamily are the only known commercial sources for these materials. Rapeseed oil as well as all other naturally occurring ester-type fats and oils suitable for greasemaking" purposes have numerous other commercial uses. Thissituation is conducive to shortages forcing undesirable variations in greasemaking procedures and grease characteristics. The present invention eliminates this difficulty.

It is, therefore, an important object of the present invention toprovide soap-thickened, good-quality, high temperature greases based on raw materials other than naturally occurring ester-type fats and oils. Another object of the invention is to provide an improved process for the production of suchgreases. Other objects and advantages will appear from the following description of the invention, read with reference to the accompanying drawing, the single figure of which is a schematic flow plan illustrating the invention.

It has now been found that high-temperature greases of excellentquality may be prepared by incorporating into lubricating oils, grease-thickening metal soaps obtained by the saponification of certain synthetic 0x0- esters formed -by reacting-mixtures of high molecular Weight olefins and low molecular weight aliphatic alcohols with CO under pressure in the presence of a cobalt catalyst. The olefins should be non-aromatic and contain at least 10, say'lO-ZO, carbon atoms per molecule, such as tetrapropylene, pentapropylene, tetrabutylene, and other polymeric olefins. 'Olefins produced from cracking operations may also be used, such as cracked petrolatum containing olefins in the range of C10 to C20, but those having an average of about 16 carbon atoms per molecule are preferred. Suitable alcohols include the low molecular weight aliphatic alcohols having 1-3 carbon atoms, such as methanol, ethanol, etc., methanol being preferred.

It has been found highly desirable to combine the grease-making soaps of high molecular weight acids obtained from Oxo-esters with suitable metal salts of low molecular weight aliphatic carboxylic acids to form soapsalt complexes of excellent high temperature qualities. These low molecular weight acids may be used in a ratio of about 1-3 mols per mol of ester. They may have l-5 carbon atoms per molecule, such as formic, acetic, propionic, butyric, valeric, furoic, acrylic acids, etc. The preferred low molecular weight acids are formic and acetic acids.

,Metal bases suitable for the formation of simple or complex grease-thickening soaps according to the present invention include the hydroxides of alkali, alkaline earth and certain other metals, such as lithium, sodium, potassium, calcium, barium and aluminum. Alkali metal hydroxides, particularly lithium and sodium hydroxides, form complex soaps of greatest stability, highest dropping point, good water resistance and excellent susceptibility to oxidation inhibition. The total soap content of the grease may be about 6-40 wt. percent. In addition to the simple and complex soaps of the invention, conventional grease making soaps of high molecular weight fatty acids having 10 to 30 carbon atoms, such as those derived from naturally occurring fatty materials,.

or suitable known grease-making salt-soap complexes may be present in proportions of up to about 50 wt. percent of the total soap content in the greases of the invention to improve high temperature or other characteristics.

Regarding suitable lubricating oil bases for greases containing the thickeners of the invention, mineral and/ or synthetic lubricating oils of all types may be used, depending on the specific grease-making method employed. When the grease-makingsoap is formed by saponification of the Oxo-ester in the lubricating oil in situ, the lubricating oil used in this stage should be non-saponifiable at the conditions involved. Mineral oils, hydrocarbon polymers and some synthetic-type lubricants which resist saponification or hydrolysis, such as high molecular Weight formals, others, etc., are suitable for this purpose. Whenever the grease-making soap is preformed and, as such, added to the lubricating oil, all types of conventional grease dispersants maybe used. Lubricating oils having good volatility characteristics are also desirable, viscosities between 60 and 200 S. S. U. at 210 R, and a viscosity index suitable (generally not over 60) for soap dispersing and crystallization are preferred. However, the viscosity index of the oil may be enhanced by later blending ina higher V. 1. oil during the grease manu facturing process. The grease-making process of the invention will now be described with reference to the drawing. The process comprises two principal stages in the first stage, i. e. the carbonylation stage designated by the reference numeral 1, ()xo-esters are prepared by subjecting mixtures of suitable olefins with low molecular alcohols of the type specified above to a catalytic carbonylation reaction with CO. The reaction may be illustrated by the equation wherein R is an alkyl group having l-3 carbon atoms and n is an integer of at least 10. Suitable reaction conditions in carbonylation stage 1 include temperatures of 25t3-500 3, preferably about 250-400 R, pressures of about 50-3000 atmospheres, preferably about-300',

.is evaporated together with the reaction water.

and olefin to alcohol mol ratios of about 1-20, preferably about -15. The catalyst may be any conventional carbonylation catalyst. Cobalt present either in the free metallic state or as a suitable compound, such as the carbonyl, .organic salt, soap, etc., is preferred. Inert diluents, such as cycle-hexane, xylene, benzene, saturated hydrocarbons,- etc., may be; employed' When soluble catalysts are used,,the ester formed is washed free of catalyst, preferably with a low molecular weight organic acid.

The product may be distilled to remove unreacted feed materials which may be recycled to the carhouylation stage. If desired, the pure acid may be recovered by hydrolysis of the ester followed by acidification, and the pure acid may then .besaponified to make the grease thickener. However, it is preferred to subject the crude ester to thesecond stage of theprocess, i. e. the saponifica- .tion and grease-making stage indicated at 2 on the drawing and :t0 recover .unreacted olefin and alcohol therefrom for recycling to the carbonylationstage l as will appearhereinafter.

The saponification stage 2 is preferably carried out in a suitable lubricating oil in situ. For this purpose, the crude or purified .Oxo-ester produced in the first stage is mixed with the lubricating oil and heated therein to about 'l30-l70 F. Thereafter, the saponifying agent, i. e. a metal base, such as alkali hydroxide, preferably in -50% aqueous solution is added and the temperature raised to about 280-325 F. When hydrolysis and saponification of the ester are complete, which is usually thecase after about l -4 hours, the temperature is raised to about 480-520 r. maximum temperature The grease may then be cooled to about 250 F. While stirring. At this point, other additives, such as oxidation inhibitors, etc., may be added, whereupon the grease may be further cooled while stirring to about l80200 F. and then poured in pans for cooling to room temperature.

Whcnit is desired to use soap-salt complexes rather than simple soaps as the thickner of the invention, a low molecular weight carboxylic acid of the type specified maybe added to the lubricating oil together with theester or after the first heating but prior to the addition of the metal base, preferablyin equi-molecular proportions with respect to the ester. Also,.any additional high molecular weight acids, such as stearic .acid, hydrogenated fish oil acids, etc., may be added in this case. The amount of metal base used should be sufficient completely to neutralize the acids present after hydrolysis, and preferably to leave a slight alkalinity or" about 0.31.0%'in the grease.

In the course of this saponification and grease-making stage proper, temperatures are employed at which all low molecular weight alcohol freedby the saponification reaction and vintroducedflas impurity of the crude Oxo-estcr The same is true for any unconverted olefin introduced into the saponification mixture together with the crude ()xoester. In accordance with a particularly advantageous embodiment of the invention, this alcohol and unconvetted olefin are passed as shown in the drawing from stage 2 to a condensation, separation and fractionation stage 3. Unconverted olefin is then recycled from stage 3 to stage 1 as indicated. Liberated alcohol may also be recovered and recycled to carbonylation stage 1, so that no fresh alcohol is required except as needed to make up for unavoidable losses. When so operating, the original olefin charge may be ultimately converted almost completely from olefin to grease in batch Operation 'or in a fully continuous-manner. This compares with a maximum olefin conversion of only about -50% in a single pass operation of the carbonylation stage. If desired, the

grease may be passed from grease-making stage 2 to a Other conventional grease additives, such as antioxidants, particularly amino compounds, extreme pressure agents containingsulfur, halogen and/ or phosphorus, etc., may be added to the grease in any conventional manner.

The invention will be further illustrated by'the following specific examples.

Example I A 3 liter bomb equipped for heating, shaking and gas pressuring was charged with: V i

775 g. C13 cracked petrolatum 635 g. methyl alcohol 9.2 g. cobalt as cobalt oleate in heptane The bomb was then closed and pressured to 2500 lbs. with C6 at room temperature. It was then heated to 302 P. where it was maintained for 21 hours. After the first hour of reaction the pressure had dropped to 1400 lbs. and the bomb was repressured with CO to 3500 lbs. 1

The product from the above reaction was washed with 10% acetic acid and then with water so as to remove the cobalt. It was then dried with Na2SO4, filtered and evaporated leaving 907 g. of crude ester having an ester number of 0.104 centi-equivalentper gram.

The crude methyl ester described above was saponified with alcoholic KOH in order to free a purified acid. The ester could have been used as such. However, the acid was isolated to determine its specific character.

After saponification the potassium soap was diluted with water and then extracted with naphtha to remove any inert materials, such as hydrocarbons. The aqueous layer was then acidified to liberate the acids which were then vacuum distilled. A heart out of acid was collected for grease manufacture. This cut had .aboiling point of 284-320 F.@ 0.7 mm. Hg.

The alkali soap from the saponification may also be used directly in the manufacture of grease.

The grease was prepared as follows:

ingredients: I Weight percent Hydrofol Acids 5.4 1 10.00 Cracked petrolatum OX0 acid (C14)... 10.00 Acetic acid 4.00 Sodium hydroxide p .650 Phenyl alpha-naphthylamine Blend of naphthenic mineral ,oils having a viscosity of S. S. U. at 210 F 68.50

Hydrogenatedfish oil acids corresponding .to stearic .acid in degree of saturation. Y

The Hydrofol Acids 54, cracked petrolatumOxo acid and /2 the mineral oil were charged to a grease kettle and warmed to F. The acetic acid wasth enadded followed immediately by a 40% aqueous solution-of sodium hydroxide. The temperature was raised to 300 F. After dehydration of the soap (i. c. after about 2 hours), the balance of the mineral oil was added and the temperature was raised to 500 F. Heating was ;then discontinued while agitating and the grease cooled to 250 F. The phenyl alpha-naphthylamine (oxidation inhibitor) wasadded and the grease further cooled while stirring to 200-l80 F.

Worked, 100,000.strokes :250. Dropping point, F .490. Water washing, percent loss 5. Norma-Hoifman oxidation, hours 1 69.

to 5 p. s. iodrop inOzpressure.

.270-ho1e worker platetig" diameter-holes.

Example 11 grease has cooled or during the cooling cycle after complete crystallization and transition of the soap below about 300 F. The grease was then homogenized to ultimate hardness by passing through a Gaulin homogenizer at 5000 p. s. i. pressure.

Properties Appearance Excellent smooth yellow grease.

Penetrations, 77 F., mm./

Unworked 290. Worked, 60 strokes 300. Worked, 67,000 strokes 375. Worked, grease rehomoge- 300.

nized.

Droping point, F 425.

Copper corrosion (3 hrs. 210 None.

F.). Water washing test, percent loss- 25. Norma-Hoifman oxidation, hours 185.

to 5 p. s. i. drop in 02 pressure.

Example 111 A 3 liter bomb equipped for heating, shaking and gas pressuring was charged with:

462 g. C13 cracked petrolatum 1420 g. methyl alcohol 2.8 g. cobalt as cobalt acetate The bomb was closed and pressured to 3800 lbs. with CO at 302 F. It was held at 302 F. for 18 hours when the final pressure had dropped to 1100 lbs.

The product from the above reaction was washed with 10% acetic acid and then with water to remove the cobalt. It was then dried with KzCOs, filtered and evaporated on the steam bath leaving 480 g. of crude methyl ester of C14 Oxo acid. Its ester number was 0.163 centiequivalents per gram, equivalent to an ester content of 38%, the remainder being unreacted olefin.

This crude methyl ester of C14 OX0 acid was used as such in the manufacture of grease, in the proportions indicated below.

The crude ester, Hydrofol Acids and /2 of the mineral oil were charged to a kettle and warmed to 150 P. Then the acetic acid was charged, followed immediately by a 40% aqueous solution of the, sodium hydroxide. Heating was continued to 300 P. where the balance of the mineral oil was added. During this heating period before the addition .of the balance of the mineral oil, water and alcohol were vaporized along with olefins that were present in the crude ester. The product was further cooled to 200 F. g

Properties:

Appearance Percent Free Alkalinity as NaOHH.

Excellent Smooth, Hard, Homogetegis Grease Penetration, 77 F., mm./l0:

Unhomog- Homogenized enized Unworked 139 167 Worked, 60 Strokes 24.6 240 Worked, 60,000 Strokes 310 Dropping Point, F 450+ Percent oss in Water Washlng Test None Norma-Hoffman Oxidation, Hours to 5 p. s. i. Drop in Pressure The present invention is not limited to the specific figures of the foregoing examples. The relative proportions of the materials used may be varied Within the limits indicated in the specification to obtain products of varying characteristics.

What is claimed is:

1. A process for making grease which comprises contacting in a carbonylation stage a non-aromatic olefin having about 10 to 20 carbon atoms with an aliphatic alcohol having about 1 to 3 carbon atoms and carbon monoxide in the presence of a carbonylation catalyst at conditions conducive to the formation of an ester of said alcohol with an acid having 1 carbon atom more than said olefin, recovering a mixture of said. ester with unconverted olefin, introducing said mixture into a mineral lubricating oil, subjecting the resulting mixture to saponification with a metal base at a grease-making temperature of about 280 to 325 F. to form a grease While driving off unconverted olefin and alcohol freed by said saponification reaction, cooling the grease and returning said unconverted olefin so driven off to said carbonylation stage, said lubricating oil being non-saponifiable at the conditions of said saponification.

2. The process of claim 1 wherein said alcohol so driven 01f is returned to said carbonylation stage.

3. The process of claim 1 wherein said grease is heated to a temperature of about 480 to 520 F. subsequent to said saponification. V

4. The process of claim 3 in which a high molecular weight fatty acid having from about 10 to 30 carbon atoms derived from naturally occurring fatty material and a low molecular weight carboxylic acid having from about 1 to 5 carbon atoms per molecule is introduced into said lubricating oil with the mixture of said ester and unconverted olefin.

, 5. The process of claim 4 wherein said high molecular weight fatty acid is hydrogenated fish oil acid and said low molecular weight carboxylic acid is acetic acid.

6. The process of claim 1 wherein said metal is selected from the group consisting of alkali metals, alkaline earth metals and aluminum.

7. The process of claim 6 wherein said metal is sodium.

References Cited in the file of this patent UNITED STATES PATENTS 2,271,619 Bradshaw et a1. Feb. 3, 1942 2,449,312 Murray et al. Sept. 14, 1948 2,468,099 Morway Apr. 26, 1949 2,470,859 Pavlic May 24, 1949 2,575,286 Morway et a1. Nov. 13, 1951 2,576,032 Morway et a1. Nov. 20, 1951 2,542,767 Gresham et a1. Feb. 20, 1951 2,594,341 Owen et al. Apr. 29, 1952 2,606,153 Holdstock Aug. 5, 1952 2,607,787 Mason Aug. 19, 1952 2,628,195 Allison et al Feb. 10, 1953 2.628.938 Whitney Feb. 17, 1953 1 12,648,694 Mason Aug. 11, 1953" 

1. A PROCESS FOR MAKING GREASE WHICH COMPRISES CONTACTING IN A CARBONYLATION STATE A NON-AROMATIC OLEFIN HAVING ABOUT 10 TO 20 CARBON ATOMS WITH AN ALIPHATIC ALCOHOL HAVING ABOUT 1 TO 3 CARBON ATOMS AND CARBON MONOXIDE IN THE PRESENCE OF A CARBONYLATION CATALYST AT CONDITIONS CONDUCIVE TO THE FORMATION OF AN ESTER OF SAID ALCOHOL WITH AN ACID HAVING 1 CARBON ATOM MORE THAN SAID OLEGIN, RECOVERING A MIXTURE OF SAID ESTER WITH UNCONVERTED OLEFIN, INTRODUCING SAID MIXTURE INTO A MINERAL LUBRICATING OIL, SUBJECTING THE RESULTING MIXTURE TO SAPONIFICATION WITH A METAL BASE AT A GREASE-MAKING TEMPERATURE OF ABOUT 280* TO 325* F. TO FORM A GREASE WHILE DRIVING OFF UNCONVERTED OLEFIN AND ALCOHOL FREED BY SAID SAPONIFICATION REACTION, COOLING THE GREASE AND RETURNING SAID UNCONVERTED OLEFIN SO DRIVEN OFF TO SAID CARBONYLATION STAGE, SAID LUBRICATING OIL BEING NON-SAPONIFIABLE AT THE CONDITIONS OF SAID SAPONIFICATION. 